-
Review ArticleMolecular Mechanism of Stem Cell Differentiation
intoAdipocytes and Adipocyte Differentiation of Malignant Tumor
Kexin Zhang,1,2 Xudong Yang,3 Qi Zhao,1 Zugui Li,1,4 Fangmei
Fu,1,4 Hao Zhang,1,4
Minying Zheng,1 and Shiwu Zhang 1
1Department of Pathology, Tianjin Union Medical Center, Tianjin,
China2Nankai University School of Medicine, Nankai University,
Tianjin, China3Tianjin Rehabilitation Center, Tianjin,
China4Graduate School, Tianjin University of Traditional Chinese
Medicine, Tianjin, China
Correspondence should be addressed to Shiwu Zhang;
[email protected]
Received 30 April 2020; Revised 7 July 2020; Accepted 27 July
2020; Published 12 August 2020
Academic Editor: Hirotaka Suga
Copyright © 2020 Kexin Zhang et al. This is an open access
article distributed under the Creative Commons Attribution
License,which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly
cited.
Adipogenesis is the process through which preadipocytes
differentiate into adipocytes. During this process, the
preadipocytes ceaseto proliferate, begin to accumulate lipid
droplets, and develop morphologic and biochemical characteristics
of mature adipocytes.Mesenchymal stem cells (MSCs) are a type of
adult stem cells known for their high plasticity and capacity to
generate mesodermaland nonmesodermal tissues. Manymature cell types
can be generated fromMSCs, including adipocyte, osteocyte, and
chondrocyte.The differentiation of stem cells into multiple mature
phenotypes is at the basis for tissue regeneration and repair.
Cancer stem cells(CSCs) play a very important role in tumor
development and have the potential to differentiate into multiple
cell lineages.Accumulating evidence has shown that cancer cells can
be induced to differentiate into various benign cells, such as
adipocytes,fibrocytes, osteoblast, by a variety of small molecular
compounds, which may provide new strategies for cancer
treatment.Recent studies have reported that tumor cells undergoing
epithelial-to-mesenchymal transition can be induced to
differentiateinto adipocytes. In this review, molecular mechanisms,
signal pathways, and the roles of various biological processes in
adiposedifferentiation are summarized. Understanding the molecular
mechanism of adipogenesis and adipose differentiation of
cancercells may contribute to cancer treatments that involve
inducing differentiation into benign cells.
1. Introduction
Adipogenesis is the process through which mesenchymalstem cells
(MSCs) commit to the adipose lineage and differ-entiate into
adipocytes. During this process, preadipocytescease to proliferate,
begin to accumulate lipid droplets, anddevelop morphologic and
biochemical characteristics ofmature adipocytes, such as
hormone-responsive lipogenesisand lipolytic programs. Currently,
there are mainly twomodels of benign adipocyte differentiation in
vitro. One isfibroid pluripotent stem cells, which can
differentiate intonot only adipocytes, but also muscle, cartilage,
and othercells. There are two kinds of fibroid pluripotent stem
cells:bone marrow and adipose mesenchymal stem cells. Anothergroup
is fibroblastic preadipocytes, which have a single direc-tion of
differentiation, namely, lipid differentiation, including
3T3-L1, and 3T3-F422A cells [1]. Cancer cells with
tumorinitiation ability, designated as cancer stem cells
(CSCs),have the characteristics of tumorigenesis and the
expressionof specific stem cell markers, as well as the long-term
self-renewal, proliferation capacity, and adipose
differentiationpotential [2]. In addition to CSCs [2], cancer cells
undergo-ing epithelial-mesenchymal transformation (EMT) havebeen
reported to be induced to differentiate into adipocytes[3–5]. Lung
cancer NCI-H446 cells can be induced to dif-ferentiate into
neurons, adipocytes, and bone cells in vitro[6]. The adipogenesis
differentiation treatment is promisingin the p53 gene deletion type
of fibroblast-derived cancer[7]. Cancer cells with homologous
recombination defects,such as ovarian and breast cancer cells with
breast cancersusceptibility genes (BRCA) 1/2 mutations, can be
inducedto differentiate by poly ADP-ribose polymerase (PARP)
HindawiStem Cells InternationalVolume 2020, Article ID 8892300,
16 pageshttps://doi.org/10.1155/2020/8892300
https://orcid.org/0000-0002-5052-2283https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2020/8892300
-
inhibitors [2]. The nuclear receptor peroxisome
proliferator-activated receptor γ (PPARγ) agonist (antidiabetic,
thiazolidi-nedione drug) can induce growth arrest and
adipogenicdifferentiation in human, mouse, and dog osteosarcoma
cells[8]. Thyroid cancer cells expressing the PPARγ fusion
protein(PPFP) can be induced to differentiate into adipocytes
bypioglitazone [9]. Adipogenesis can be induced in
well-differentiated liposarcoma (WDLPS) and
dedifferentiatedliposarcoma (DDLPS) cells by dexamethasone,
indomethacin,insulin, and 3-isobutyl-1-methyl xanthine (IBMX)
[10].
In this review, we highlight some of the crucial transcrip-tion
factors that induce adipogenesis both in MSCs and inCSCs, including
the well-studied PPARγ and CCAATenhancer-binding proteins (C/EBPs)
[11], as well as othercell factors that have been recently shown to
have an impor-tant role in adipocyte differentiation. We focus on
under-standing the complex regulatory mechanism of
adipocytedifferentiation that can contribute to the clinical
treatmentof human diseases, including those caused by obesity
andadipocytes dysfunction, especially for the malignant tumor,which
can be transdifferentiated into mature adipocytes.
2. Adipocyte Differentiation
Cell proliferation and differentiation are two
opposingprocesses, and there is a transition between these two
pro-cesses in the early stages of adipocyte differentiation.
Theinteraction of cell cycle regulators and differentiation
fac-tors produces a cascade of events which ultimately resultsin
the expression of adipocyte phenotype [7]. Adipogenesishas
different stages. Each stage has a specific gene expres-sion
pattern [12]. In general, adipocyte differentiation ofpluripotent
stem cells is divided into two phases. The firstphase, known as
determination, involves the commitment ofpluripotent stem cells to
preadipocytes. The preadipocytescannot be distinguished
morphologically from their precur-sor cells, but also have lost the
potential to differentiate intoother cell types. In the second
phase, which is known asterminal differentiation, the preadipocytes
gradually acquirethe characteristics of mature adipocytes and
acquire physio-logical functions, including lipid transport and
synthesis,insulin sensitivity, and the secretion of
adipocyte-specificproteins [13].
The differentiation of precursor adipocytes is also dividedinto
four stages: proliferation, mitotic cloning, early
differen-tiation, and terminal differentiation [14]. After the
precur-sors are inoculated into the cell culture plates, the
cellsgrow exponentially until they converge. After reaching
con-tact inhibition, the growth rate slows and gradually
stagnates,and the proliferation of precursor adipocytes stops,
which isvery necessary for initiating the differentiation of
precursoradipocytes. Adipocyte precursors exhibit transient
mitosis,called “clonal expansion,” a process that relies on the
actionof induced differentiation factors. Some preadipocyte
cells(mouse cell lines 3T3-L1, 3T3-F442A) undergo one or tworounds
of cell division prior to differentiation [15], whereasother cell
lines (mouse C3H10T1/2) differentiating into adi-pocyte do not
undergo mitosis clonal expansion [16].Whether “mitotic clonal
expansion” is required for adipose
differentiation remains controversial. However, it is
certainthat some of the checkpoint proteins for mitosis
regulateaspects of adipogenesis [7, 17]. When cells enter the
terminaldifferentiation stage, the de novo synthesis of fatty
acidsincreases significantly, the transcription factors and
adipocyte-related genes work cooperatively to maintain precursor
adipo-cyte differentiation into mature adipocytes containing
largelipid droplets [1].
3. Regulatory Pathways inPreadipocytes Commitment
Adipocyte differentiation is a complex process in which
geneexpression is finely regulated. The most basic regulatory
net-work of adipose differentiation has not been updated inrecent
years, but some factors and signaling pathways thatdo affect
adipose differentiation have been continuouslyreported. Adipocyte
differentiation is the result of the geneexpression that determines
the phenotype of adipocytes,which is a complex and delicate
regulatory process (Figure 1).
3.1. Wnt Signal Pathway in Adipogenesis. Wnt signaling
isimportant for adipocytes proliferation and differentiationboth in
vitro and in vivo [18]. The Wnt family of secretedglycoproteins
functions through paracrine and autocrinemechanisms to influence
cell fate and development. Wntprotein binding to frizzled receptors
initiates signalingthrough β-catenin-dependent and -independent
pathways[19]. Wnt signaling inhibits adipocyte differentiation in
vitroby blocking the expression of PPARγ and C/EBPα [20].
Con-stitutive Wnt10b expression inhibits adipogenesis. Wnt10b
isexpressed in preadipocytes and stromal vascular cells, butnot in
adipocytes. In vivo, transgenic expression of Wnt10bin adipocytes
results in a 50% reduction in white adipose tissuemass and absent
brown adipose tissue development [21].Wnt10a and Wnt6 have also
been identified as determinantsof brown adipocyte development [22,
23]. Wnt5b is tran-siently induced during adipogenesis and promotes
differentia-tion [24], indicating that preadipocytes integrate
inputs fromseveral competing Wnt signals.
3.2. The Hedgehog (HH) Signaling Pathway Mechanism.Three
vertebrate HH ligands including sonic hedgehog(SHH), Indian
hedgehog (IHH), and desert hedgehog(DHH) have been identified and
initiated a signaling cascademediated by patched (Ptch-1 and
Ptch-2) receptors [25, 26].HH signaling had an inhibitory effect on
adipogenesis inmurine cells, such as C3H10T1/2, KS483, calvaria
MSCslines, and mouse adipose-derived stromal cells [27]. Thesecells
were visualized by decreased cytoplasmic fat accumula-tion and the
expression of adipocyte marker genes after HHsignaling was
inhibited [28]. Although it is generally agreedthat HH expression
has an inhibitory effect on preadipocytedifferentiation, the
mechanisms linking HH signaling andadipogenesis remain poorly
defined [29].
3.3. ERK/MAPK/PPAR Signal Pathway. Extracellular-regu-lated
protein kinase (ERK) is required in the proliferativephase of
differentiation. ERK activity blockade in 3T3-L1
2 Stem Cells International
-
cells and embryonic stem cells can inhibit adipogenesis. Inthe
terminal differentiation phase, ERK1 activity leads toPPARγ
phosphorylation, which inhibits adipocyte differenti-ation. This
implies that ERK1 activity must be reduced afteradipocyte
proliferation so that differentiation can proceed.This reduction is
mediated in part by mitogen-activatedprotein kinase (MAPK)
phosphatase-1 (MKP1) [30, 31].These extracellular and intracellular
regulation factors causeadipocyte-specific gene expression and
eventually lead toadipocyte formation.
4. Adipocyte DifferentiationRegulatory Proteins
4.1. PPARγ and Adipocyte Differentiation. PPARγ is a mem-ber of
the nuclear-receptor superfamily and is both necessaryand
sufficient for adipogenesis [32]. Forced expression ofPPARγ is
sufficient to induce adipocyte differentiation infibroblasts [33].
Indeed, the proadipogenic C/EBPs andKrüppel-like factors (KLFs)
have all been shown to induceat least one of the two PPARγ
promoters. In contrast, antia-dipogenic transcription factor GATA
functioned in part byrepressing PPARγ expression [34]. PPARγ itself
has twoisomers. The relative roles of PPARγ1 and PPARγ2 in
adipo-genesis remain an open question. PPARγ2 is mainlyexpressed in
adipose tissue, while PPARγ1 is expressed inmany other tissues.
Although both can promote adipocytedifferentiation, PPARγ2 could do
so effectively at very lowligand concentration compared with PPARγ1
[35]. The twoprotein isoforms are generated by alternative splicing
andpromoter usage, and both are induced during adipogenesis.PPARγ1
can also be expressed in cell types other than adipo-cytes. Ren et
al. [36] used engineered zinc-finger proteins to
inhibit the expression of the endogenous PPARγ1 andPPARγ2
promoters in 3T3-L1 cells. Ectopic expression ofPPARγ2 promotes
adipogenesis, whereas that of PPARγ1does not. Zhang et al. reported
that PPARγ2 deficiencyimpairs the development of adipose tissue and
insulin sensi-tivity [37].
There are transcriptional cascades between adipocytesgenes,
including PPARγ and C/EBPα which are the coreadipocyte
differentiation regulators. In the early stage of adi-pocyte
differentiation, the expression of C/EBPβ and C/EBPδincrease, which
upregulates C/EBPα expression, furtheractivate PPARγ. PPARγ
activating C/EBPα in turn resultsin a positive feedback. PPARγ
binding with retinoic acid Xreceptor (RXR) forms different
heterodimers. The variousdimmers can combine with the PPARγ
response element(PPRE) and initiate the transcription of downstream
genesfor differentiation into adipocytes [38].
C/EBPs participate in adipogenesis, and several C/EBPfamily
members are expressed in adipocytes, includingC/EBPα, C/EBPβ,
C/EBPγ, C/EBPδ, and C/EBP-homolo-gous protein (CHOP). The temporal
expression of thesefactors during adipocyte differentiation
triggers a cascadewhereby early induction of C/EBPβ and C/EBPδ
leads toC/EBPα expression. This notion is further supported by
thesequential binding of these transcription factors to
severaladipocyte promoters during adipocyte differentiation.C/EBPβ
is crucial for adipogenesis in immortalized preadi-pocyte lines.
C/EBPβ and C/EBPδ promote adipogenesis atleast in part by inducing
C/EBPα and PPARγ. C/EBPαinduces many adipocyte genes directly and
plays an impor-tant role in adipose tissue development. Once C/EBPα
isexpressed, its expression is maintained through autoactiva-tion
[39]. Despite the importance of C/EBPs in adipogenesis,
DEX, insulin, DEMX
Testosterone
𝛽-catentin
CEBP𝛽SREBP
MAPKG3K-3𝛽
P2-C/EBP𝛽
WNT 10band others SHH TGF𝛽
BMPs
SMAD1
- SMAD3 SMAD3
PI3K
CREB
P-CREB
AKT
FOXO1/A2 TCF/LEF GATA2/3
Adipocytegenes
PBC SMO
AR
IRS
PPARΎ
C/EBPα
P
PKA
Figure 1: Regulation pathways in preadipocytes commitment. BMP
and Wnt families are mediators of MSCs commitment to
producepreadipocytes. Exposure of growth-arrested preadipocytes to
differentiation inducers (IGF1, glucocorticoid, and cAMP) triggers
DNAreplication, leading to adipocyte gene expression due to a
transcription factor cascade. The dotted line indicates an
uncertain molecularregulatory mechanism.
3Stem Cells International
-
these transcription factors clearly cannot function
efficientlyin the absence of PPARγ. C/EBPβ cannot induce
C/EBPαexpression in the absence of PPARγ, which is required
torelease histone deacetylase-1 (HDAC1) from the C/EBPαpromoter
[40]. Furthermore, ectopic C/EBPα expressioncannot induce
adipogenesis in PPARγ–/– fibroblasts [41].However, C/EBPα also
plays an important role in differenti-ated adipocytes.
Overexpression of exogenous PPARγ inC/EBPα-deficient cells showed
that, although C/EBPα isnot required for lipid accumulation and the
expression ofmany adipocyte genes, it is necessary for the
acquisition ofinsulin sensitivity [42, 43] (Figure 2). Human
fibroblasts withthe ability to differentiate into adipocytes also
do not undergomitotic cloning amplification. However, PPARγ
exogenousligands need to be added to promote adipocyte
differentia-tion. Therefore, it can be inferred that mitotic
cloning expan-sion can produce endogenous ligands of PPARγ [7].
4.2. BMP and Transforming Growth Factor β (TGF-β) inAdipocyte
Differentiation. A variety of extracellular factorsaffect the
preadipocyte commitment of stem cells, includingbone morphogenetic
protein (BMP) [44], transforminggrowth factor β (TGF-β) [45],
insulin/insulin-like growthfactor 1 (IGF1) [46], tumor necrosis
factor α and interleukin1 β [47], matrix metalloproteinase 2 [48],
fibroblast growthfactor (FGF) 1, and FGF2 [49]. BMP and TGF-β have
variedeffects on the differentiation fate of mesenchymal cells
[50].The TGF-β superfamily members, BMPs, and myostatinregulate the
differentiation of many cell types, includingadipocytes [51]. TGF-β
inhibitor can promote adipose differ-entiation of cancer cells with
a mesenchymal phenotypein vitro, and transgenic overexpression of
TGF-β impairsadipocyte development [3]. Inhibition of adipogenesis
couldbe obtained through blocking of endogenous TGF-β with
adominant-negative TGF-β receptor or drosophila mothersagainst
decapentaplegic protein (SMAD) 3 inhibition.SMAD3 binds to C/EBPs
and inhibits their transcriptionalactivity, including their ability
to transactivate the PPARγ2promoter [52, 53]. Exposure of
multipotent mesenchymalcells to BMP4 commits these cells to the
adipocyte lineage,allowing them to undergo adipose conversion [50].
Theeffects of BMP2 are more complex and depend on the pres-ence of
other signaling molecules. BMP2 alone has little effecton
adipogenesis, and it interacts with other factors such asTGF-β and
insulin to stimulate adipogenesis of embryonicstem cells [54]. BMP2
stimulates adipogenesis of multipotentC3H10T1/2 cells at low
concentrations and can contribute tochondrocyte and osteoblast
development at higher concen-trations [55].
4.3. KLFs in Adipocyte Differentiation. During adipocyte
dif-ferentiation, some KLF family members are overexpressed,such as
KLF4, KLF5, KLF9, and KLF15, while KLF16 expres-sion is reduced
[56, 57]. KLF15 is the first KLF family mem-bers, which were
identified to be involved in adipocytedifferentiation. Its
expression increased significantly on thesixth day of 3T3-L1
adipocyte differentiation and peakedon the second day of adipocyte
induction in MSCs andmouse embryonic fibroblasts. Inhibition of
KLF15 by siRNA
or mutation led to a decrease in PPARγ, CEBPα, fatty
acid-binding protein 4 (FABP4), and glucose transporter 4(GLUT4).
However, overexpression of KLF15 in NIH3T3cells was found to be
associated with lipid accumulation aswell as increases in PPARγ and
FABP4 [58]. Mice with com-plete absence of KLF5 showed embryonal
lethality, and micewith single-chromosome KLF5 knockout showed a
signifi-cant reduction in white fat in adulthood, suggesting
thatKLF5 plays an important role in adipocyte differentiation.KLF5
can be activated by C/EBPβ or C/EBPδ, which isinvolved in early
adipocyte differentiation. KLF5 can beactivated by C/EBPβ or
C/EBPδ, which is involved in earlyadipocyte differentiation. Direct
binding of KLF5 to thePPARγ2 promoter in combination with C/EBPs
inducesPPARγ2 expression [59]. Transfection of KLF5
dominant-negative mutants in 3T3-L1 cells reduced lipid droplet
accu-mulation and inhibited PPARγ and C/EBPα expression,whereas
overexpression of wild KLF5 significantly promotedadipocyte
differentiation, even without exogenous hormonestimulation. Similar
to KLF5, KLF9 knockdown can inhibitthe expression of a series of
adipocyte differentiation genes,such as PPARγ, C/EBPα, and FABP4,
hence inhibitingadipocyte differentiation. However, KLF9
overexpressiondid not upregulate the expression of PPARγ and
C/EBPα[60]. In addition, KLF4 can transactivate C/EBPβ by bindingto
the region of 1438-1134KB upstream of the C/EBPβ pro-moter and
promote lipid differentiation [61]. KLF6 can forma complex with
histone deacetylase-3 (HDAC3), inhibitingpreadipocyte factor-1
(Pref-1) expression and promotinglipid differentiation [62]. KLF2
is highly expressed in adiposeprogenitors, and its expression
decreases during the processof lipid differentiation. Overexpressed
KLF2 can bind to theCACCC region of PPARγ2 proximal promoter and
inhibitlipid differentiation as well as the expression of
PPARγ,C/EBPα, and sterol-regulated element-binding proteins(SREBP)
by inhibiting the promoter activity [63]. RNAsequence analysis
showed that KLFl6 expression wasdecreased on the first day of
adipocyte differentiation of3T3-L1 cells. Adipocyte differentiation
was promoted byKLF16 knockdown but was inhibited by KLF16
overexpres-sion via inhibition of PPARγ promoter activity [64]. In
addi-tion, KLF3 and KLF7 were also found to play a
negativeregulatory role in adipocyte differentiation [65, 66].
4.4. Signal Transducers and Activators of Transcription(STATs)
and Adipocyte Differentiation. The activated STATprotein enters the
nucleus as a dimer and binds to the targetgene to regulate gene
transcription. In the adipocyte differen-tiation of mouse 3T3-L1
cells, the expression of STAT1 andSTAT5 was significantly
increased, while that of STAT3and STAT6 was not significantly
changed [67]. In the adipo-cyte differentiation of human
subcutaneous adipose precur-sor cells, STAT1 expression was
significantly decreased[68], while the expression of STAT3 and
STAT5 wasincreased and STAT6 expression was unchanged [69]. Therole
of STAT1 in adipocyte differentiation is not clear,because its
expression trend in humans and mice differsduring the adipocyte
differentiation process. Early adipocytedifferentiation of 3T3-L1
cells was inhibited by STAT1
4 Stem Cells International
-
agonist interferon γ. Loss of STAT1 in 3T3-L1 cells can res-cue
the inhibition of adipocyte differentiation caused byprostaglandin
factor 2α [70]. Other studies have found thatSTAT1 is required for
adipose differentiation, and STAT1overexpression in C3H10T1/2 cells
can prevent the inhibi-tion of lipid differentiation caused by
B-cell lymphoma-6knockdown [71]. There was no abnormal adipose
tissuein STAT1 knockout mice [72]. STAT3 not only affectsthe
proliferation of 3T3-L1 cells but also coregulates theiradipocyte
differentiation with high mobility group protein2 [73]. The FABP4
promoter was used to specificallyknock out STAT3 in the adipose
tissue of mice, and theresults showed that mice weight
significantly increasedand the adipocyte quantity increased
compared with thewild-type mice [74]. STAT5A and STAT5B have
differenteffects on adipocyte differentiation. Abnormal adipose
tissuewas found in the mice with STAT5A or STAT5B knockout ordouble
knockout, and the amount of adipose tissue was onlyone-fifth of the
original adipose tissue in mice withoutknockdown [75].
4.5. Histone Modification in Adipocyte Differentiation. His-tone
deacetylase sirtuin (SIRT) 1 plays an important rolein biological
processes such as stress tolerance, energymetabolism, and cell
differentiation [76]. During the adi-pocyte differentiation of
C3H101/2 cells, SIRT1 expressiondecreased [77]. Overexpression of
SIRT1 activated theWnt signal, which caused the deacetylation of
β-catenin.The accumulation of β-catenin in the nucleus could
inhibitadipocyte differentiation. SIRT1 knockdown resulted
inincreased acetylation of the histones H3-K9 and H4-K16 inthe
secreted frizzled-related protein (sFRP) 1 and sFRP2 pro-moters,
thereby promoting transcription of these genes andpromoting lipid
differentiation [78]. Forkhead box proteinO (FOXO) 1 is a member of
the transcription factor FOXOfamily. It can recruit cyclic AMP
response element-bindingprotein (CBP)/histone acetyltransferase
p300 to initiate anacetylation. The acetylated FOXO1 can be
phosphorylatedby phosphorylated protein kinase B (PKB/AKT). The
phos-phorylation of FOXO1 by AKT inhibits the transcriptional
activation of FOXO1. The acetylation of FOXO1 lost the abil-ity
of DNA-binding affinity and promoted its shuttling fromnuclei to
cytoplasm [79]. SIRT1 and SIRT2 can deacetylateand active FOXO1.
Activated FOXO1 (nonphosphorylatednuclear FOXO1) in the nucleus
binds to the promoters of tar-get genes encoding p21, p27, and
PPARγ, and initiates subse-quent transcriptions [80]. SIRT2
inhibits the acetylation andphosphorylation of FOXO1, thereby
induces the accumula-tion of activated FOXO1 in the nucleus.
Activated FOXO1could inhibit adipogenesis via PPARγ [81–84].
Lysine-specific histone demethylase 1 (LSD1) expression
increasedduring the adipocyte differentiation of 3T3-L1 cells.
LSD1could reduce the dimethylation levels of histone H3K9 andH3K4
in the C/EBPα promoter region, thereby promotingadipocyte
differentiation [85]. SET domain-containing 8(SETD8) catalyzed the
monomethylation of H4K20 andpromoted PPARγ expression. The
activation of PPARγ tran-scriptional activity leads to the
induction of monomethylatedH4K20 and modification of PPARγ and its
targets, therebypromoting adipogenesis [86]. Enhancer of zeste
homolog 2(EZH2) is a methyltransferase and can bind methyl groupsto
histone H3K27, which is also necessary for lipid differenti-ation.
The absence of EZH2 in brown fat precursors results inreduced
levels of the Wnt promoter histone H3K27me3,which is also saved by
the ectopic EZH2 expression or theuse of a Wnt/β-catenin signal
inhibitor [87]. In addition, his-tone demethylases such as
lysine-specific histone demethy-lase (LSD/KDM) 4, KDM6, and histone
lysine demethylasePHF2 are also involved in adipose
differentiation, andKDM2B inhibits transcription factor activator
protein 2αpromoter via H3K4me3 and H3K36me2 [88].
5. Role of microRNA and Long NoncodingRNA in Adipogenesis
microRNA (miR) can bind and cut target genes or inhibittarget
gene translation. Endogenous siRNA can be producedby the action of
Dicer enzyme and bind to a specific proteinto change its cellular
location [89]. Many kinds of miRsare involved in regulating
adipocyte differentiation. The
Genes of terminaladipocytedifferentiation
CHOP
C/EBPΎ
KLF2
GATA2/3
KROX20
KLF5 KLF15SREBP1c
PPARΎC/EBP𝛽
C/EBP𝛿C/EBP𝛼
Ligand
Anti-adipogenicPro-adipogenic
Figure 2: A cascade of transcription factors that regulate
adipogenesis. PPARγ is one of the key transcription factors in
adipogenesis and thecore of the transcriptional cascade that
regulates adipogenesis. PPARγ expression is regulated by several
proadipogenic (blue) andantiadipogenic (red) factors. C/EBPα is
regulated through a series of inhibitory protein–protein
interactions. Some transcription factorfamilies include several
members that participate in adipogenesis, such as the KLFs. Black
lines indicate effects on gene expression; violetlines represent
effects on protein activity.
5Stem Cells International
-
expression of miR-143 increased during the differentiationof
adipose progenitor cells. Overexpression of miR-143promoted gene
expression involved in adipose differentiationand triglyceride
accumulation. Inhibition of miR-143 pre-vented the adipose
differentiation of human fat progenitorcells [90, 91].
Additionally, miR-8 promotes adipocyte differ-entiation by
inhibiting Wnt signaling [92]. Moreover, miR-17-92, miR-103,
miR-21, miR-519d, miR-210, miR-30,miR-204/211, and miR-375 also
play a certain role in pro-moting adipocyte differentiation, while
miR-130, miR-448,and let-7y inhibit lipid differentiation [93, 94].
In additionto miRs, long noncoding RNA (LncRNA) is a type of
non-coding RNA and is important during epigenetic regulationand can
form a double-stranded RNA complex with mRNAcauses protein
transcription. Lnc-u90926 inhibits adipocytedifferentiation by
inhibiting the transactivation of PPARγ2[95]. As a novel LncRNA,
HOXA-AS3 expression increasedduring the adipose differentiation of
MSCs, and HOXA-AS3 silencing reduced the marker gene of adipose
differenti-ation and inhibited the adipose differentiation [96].
Zhu et al.[97] reported that HOXA-AS3 interacted with EZH2
toregulate lineage commitment of MSCs. HOXA -AS3 canregulate the
trimethylation level of H3K27 in the Runx2promoter region by
binding to EZH2. Therefore, HOXA-AS3 is considered to be an
epigenetic switch regulating MSCslineage specificity [98].
Adipocyte differentiation-associatedLncRNA can act as a competitive
endogenous RNA of miR-204 in the process of lipid differentiation,
thereby promotingthe expression of SIRT1, the target gene of
miR-204, and thusinhibiting lipid differentiation [99]. The LncRNA
NEAT1can also regulate adipocyte differentiation under the
influ-ence of miRNA140 [100]. Other LncRNA including LncRNABlnc1
and Plnc 1 are also involved in regulating adipocytedifferentiation
[101, 102].
6. Other Biochemical Response Involved inAdipocyte
Differentiation
6.1. Unfolded Protein Responses in Adipocyte Differentiation.In
the endoplasmic reticulum of eukaryotes, unfolded pro-tein response
involves three proteins: inositol-requiringenzyme 1α,
double-stranded RNA-dependent proteinkinase-like ER kinase, and
activating transcription factor(ATF) 6α [103]. Knockdown of ATF6α
affects the expressionof adipocytes genes and inhibits C3H10T1/2
adipocyte dif-ferentiation [104]. The inhibitory effect of
berberine on adi-pocyte differentiation of 3T3-L1 cells is also due
to inducedCHOP and decorin 2 expressions, and this inhibitory
effectis ameliorated by CHOP knockout [105]. In the
adipocytedifferentiation process of 3T3-L1 cells, increases in
PPARγand C/EBPα as markers of adipocyte differentiation
wereaccompanied by an increase in the corresponding
proteinexpressions of phosphorylated Eukaryotic translation
initia-tion factor (EIF) 2α, phosphorylated endoribonucleaseIRE1α,
ATF4, CHOP, and other unfolded protein responses.Endoplasmic
reticulum stress inducer or hypoxic endoplas-mic reticulum stress
can inhibit adipocyte differentiation.Additionally, EIF2α mutation
results in continuous activa-tion or overexpression of CHOP, which
also inhibits adipo-
cyte differentiation [106]. After the initiation of
adiposedifferentiation, numerous differentiation-associated
proteinsare synthesized. Exogenous endoplasmic reticulum
stressinducers can lead to excessive endoplasmic reticulumresponse,
which in turn affects the synthesis of proteinsrelated to
differentiation and inhibits adipocyte formation(Figure 3).
6.2. Role of Oxidative Stress in Adipogenesis. During
thedirectional differentiation of MSCs, mitochondrial complexI and
III, and NADPH oxidase NOX4 are the main sourcesof oxygen species
(ROS) production. Currently, it is believedthat ROS affects not
only the cell cycle and apoptosis but alsodifferentiation through
influencing the signaling pathwaysincluding the Wnt, HH, and FOXO
signaling cascade duringMSCs differentiation [107]. The
differentiation ability ofstem cells is determined by the
arrangement of perinuclearmitochondria, which specifically
manifests as low ATP/cellcontents and a high rate of oxygen
consumption. The lackof these characteristics indicates stem cell
differentiation[108]. Adipocyte differentiation is a highly
dependent ROSactivation factor related to mitosis and cell
maturation[109]. Schroder et al. found that exogenous H2O2 could
stim-ulate adipocyte differentiation of mouse 3T3-L1 cells andhuman
adipocyte progenitor cells in the absence of insulin.H2O2 regulates
adipocyte differentiation of 3T3-L1 cells ina dose-dependent
manner. High doses of H2O2 (1, 10, and30μM) promote adipocyte
differentiation [110, 111]. Tor-mos et al. found that ROS synthesis
increased in humanMSCs at the early stage of adipose
differentiation, and tar-geted antioxidants could inhibit lipid
differentiation. Byknocking down Rieske iron-sulfur protein and
ubiquinone-binding protein, ROS produced by mitochondrial
complexIII was found to be necessary in initiating adipose
differenti-ation [112]. However, other studies have shown that
theexpression levels of adiponectin and PPARγ were decreasedby
using H2O2 (0.1–0.5mM) in 3T3-L1 cells [113]. Free rad-ical nitric
oxide (NO) also promotes lipid differentiation,because treatment
with NO inducer hydroxylamine or NOsynthase (NOS) substrate
arginine can significantly induceadipose differentiation of rat
adipose progenitor cells. NOSinduced adipose differentiation mainly
via eNOS rather thaniNOS [114]. ROS can induce adipose
differentiation primar-ily by inhibiting Wnt, FOXO, and HH
signaling pathwaysthat inhibit lipid differentiation.
6.3. Autophagy in Adipocyte Differentiation. The increase
inautophagosomes during lipid differentiation indicates
thatautophagy may play an important role in lipid
differentiation[115]. Baerga et al. confirmed that the adipocyte
differentia-tion efficiency was significantly inhibited in mouse
embry-onic fibroblasts lacking autophagy-related gene (Atg) 5,
agene encoding an essential protein required for autophagy[116].
Knockdown of Atg5 in 3T3-L1 cells promotesproteasome-dependent
degradation of PPARγ2, therebyinhibiting adipocyte differentiation
[117]. Zhang reportedthat autophagy-related gene 7(Atg7) is also
crucial for adi-pose development. Atg7-deficient mice were slim and
onlyhad 20% of white fat compared to wild-type mice, and the
6 Stem Cells International
-
lipid metabolism and hormone-induced lipolysis in the
adi-pocytes were altered [118]. Autophagy related gene Atg4b
isactivated by C/EBPβ in the process of lipid differentiation,and
autophagy activation is necessary for the degradation
of Klf2 and Klf3, two negative regulators of lipid
differentia-tion. These results showed that adipose differentiation
andautophagy are mutually complementary [119]. In 3T3-L1cells,
autophagy was inhibited by aspartate ammonia or 3-
CEBP𝛽 geneKLF4
EGR2
CEBP𝛽
CEBP𝛿 gene
EBF1 gene
CEBP𝛿EBF1
KLF5gene
KLF5
AIDRF
ZNF638
ZNF467NR2F2
NFKB1(1-433):RELA
SREBF1A,2
PPARΎ gene
PPARΎRXRA
PPARΎ:RXRA heterodimer
NCOR1HDAC3NCOR2
PPARΎ:RXRA:corepressor complexFABP4:Ligands of PPARΎ
FAM120B
NCOA2
THRAP3
EP300
HELZ2NCOA3
PPARGC1ACREBBP
NCOA1
Mediator complex (consensus)
PPARΎ:fatty acid:RXRA:mediator:coactivator complex
FABP4
CEBP𝛼
ADIPOQ gene
SLC2A4 gene(GLUT4 gene)
LEP gene
FABP4 gene
CDK4
CCND3PLIN1 gene
PCK1 gene
CD36 gene
ANGPTLgene
LPL gene
PPARA:RXRAcoactivator complex
FABP4
PCK1
PLIN1
TGF𝛽1
TNF(77-233)
WNT1,WNT10B
ADIPOQ
GLUT4/SLC2A4 tetramer
LEP
ANGPTL4
LPL
4xPalmC-CD36Pa Pa PaPa
Transcription of genes into proteinsProteins bind to gene
promoters
Cytosol
Nucleoplasm
lipid droplet
Acting on proteins, compounding
CEBP𝛼 gene
Figure 3: Regulation of adipocyte differentiation. A regulatory
loop exists between PPARγ and CEBP activation. Transcription factor
Coe(EBF) activates CEBPα, CEBPα activates EBF1, and EBF1 activates
PPARγ. CEBPβ and CEBPδ act directly on the PPARγ gene bybinding its
promoter and activating transcription. CEBPα, CEBPβ, and CEBPδ can
activate the EBF1 gene and KLF5. The EBF1 and KLF5proteins in turn
bind the promoter of PPARγ, which becomes activated. Other
hormones, such as insulin, can affect the expression ofPPARγ and
other transcription factors, such as SREBP1c. PPARγ can form a
heterodimer with the RXRα. In the absence of activatingligands, the
PPARγ-RXRα complex recruits transcription repressors, such as
nuclear receptor corepressor (NCoR) 2, NCoR1, andHDAC3. Upon
binding with activating ligands, PPARγ causes a rearrangement of
adjacent factors. Corepressors such as NCoR2 are lost,and
coactivators such as Transcription intermediary factor TIF2, CBP,
and p300 are recruited, which can result in the expression of
CyclicAMP-responsive element-binding protein (CREB) followed by
PPARγ. PPARγ expression initiates the expression of downstream
genes,including angiopoietin-related protein PGAR, Perilipin,
FABP4, CEBPα, fatty acid transport-related proteins, carbohydrate
metabolism-related proteins, and energy homeostasis-related
proteins.
7Stem Cells International
-
methyladenine at different lipid induction periods (0–2,
2–4,4–6, and 6–8 days), and only autophagy inhibition at 0–2days
hindered the formation of lipid droplets and the expres-sion of
lipid marker genes, indicating that autophagy wasvery important in
the early stage of lipid differentiation[120]. Recent studies
showed that LC3 is overexpressed in3T3-L1 cells, further
demonstrating the important role ofautophagy in lipid
differentiation [121].
6.4. Role of Alternative Splicing in Adipogenesis.
Selectivesplicing is influenced by splicing regulators, which
regulateadipocyte differentiation by regulating the selective
splicingof genes specific to this process. Lipin1 is an important
regu-lator in the process of adipocyte differentiation and
includestwo isomers, Lipin1α and Lipin1β, which have
differenteffects. High expression of Lipin1α promotes adipocyte
dif-ferentiation, while that of Lipin1β promotes lipid droplet
for-mation [122]. In Sam68-deficient mice, the fifth intron
ofserine/threonine-protein kinase mTOR was retained, result-ing in
unstable and rapid mTOR degradation and inhibitionof adipocyte
differentiation [123]. Furthermore, there arefour isomers of
Pref-1, Pref-1a and Pref-1b can inhibit adipo-cyte differentiation
of 3T3-L1, while Pref-1c and Pref-1dhave no effect on this process
[124].
6.5. Cytoskeletal Remodeling in Adipocyte Differentiation.During
adipocyte differentiation from stem cells, morpho-logical changes
to cells due to remodeling of the actin cyto-skeleton are the
hallmark of differentiation. McBeath et al.showed that cell shape
was associated with differentiationof human MSCs to adipocytes or
osteoblasts. Flattened andspread cells underwent osteogenesis,
while unspread, roundcells became adipocytes. They demonstrated
that mesenchy-mal cells mainly from mesoderm cells were more prone
toadipocyte differentiation, while pinacocytes were more proneto
osteogenic differentiation. Disruption of actin by cytocha-lasin D
can significantly promote adipocyte differentiation[125]. The
increase in the monomer G-actin interacts withmegakaryoblastic
leukemia 1 and inhibits its nuclear translo-cation, thereby
promoting PPARγ expression during adipo-cyte differentiation [126],
while the mTORC2 signal andRhoA-ROCK mediate cytoskeletal
remodeling and MSCslineage selection [127]. During adipocyte
differentiation, theformation of cortical actin structures starts
with the accumu-lation of filamentous actin near the cell membrane.
The cor-tical assembly and nucleation of actin are controlled by
theactin-related protein 2/3 (Arp2/3) complex. Yang et al.
foundthat Arp2/3 knockdown seriously inhibited adipocyte
differ-entiation of cells, and the cortical actin cytoskeleton was
veryimportant for the secretion of GLUT4 particles into cells
aswell as insulin signal transduction [128].
7. Adipose Differentiation Induction ofMalignant Tumor Cells
Tumors are considered to be heterogeneous ecosystems com-posed
of a variety of tumor cell subsets and stromal cells.Cancer cells
are typically characterized by uncontrolled pro-liferation and
disorders of differentiation. The long-term self-
renewal, proliferation capacity, and differentiation potentialof
CSCs are considered to be the major determinants oftumor
recurrence, treatment failure and metastasis,
andchemotherapy-resistant [129]. Only one subset of tumor cellscan
drive tumorigenesis and initiate the formation of hetero-geneous
tumors. It is important to note that any cell in thetumor may gain
or lose its initiation-ability due to tumormicroenvironment or
therapeutic interventions. Therefore,CSCs should be considered as a
state cell rather than a staticsubpopulation of cancer cells [130,
131]. Adipose differentia-tion of human MSCs could be induced by
using a complexstimulus which includes dexamethasone,
3-isobutyl-1-meth-ylxanthine, indomethacin, and insulin (a
classical cocktail)[132]. Our previous study has shown that
polyploid giantcancer cells (PGCCs) had the properties of CSCs and
canbe induced into adipose in vitro and in vivo [133].
7.1. Malignant Tumor Cells Can Be Induced Adipocytes.WDLPS and
dedifferentiated DDLPS are the most commontypes of liposarcoma.
WDLPS/DDLPS cells can be inducedto differentiate into adipocytes by
dexamethasone, indo-methacin, insulin, and IBMX. In vitro
experiments haveshown that these four compounds induce adipogenesis
byupregulation of transcription and translation of genesinvolved in
maintaining cancer cell stemness and adipogenicdifferentiation,
which might be used in the clinical treatmentof DDLPS patients in
the future [10]. In vivo, the induction ofadipogenesis inhibited
the tumorigenic ability of DDLPS.The tumor suppressor protein p53
is the negative regulatorof adipocyte formation and the positive
regulator of insulinsensitivity [134]. In theory,
adipocyte-inducing agent canresult in the least partial
differentiation of tumor cells, reduc-ing their malignant phenotype
in p53 deficient tumors. Theadipogenic differentiation potential is
promising in the treat-ment of cancer cell-derived from p53
deletion fibroblast.
7.2. Adipocyte Differentiation of CSCs. CSCs are a verysmall
population of cancer cells that exist in tumor tissueand closely
related to the occurrence, development, metas-tasis, recurrence,
and drug resistance of malignant tumors[135]. Adipocytes can derive
not only from preadipocytesand pluripotent MSCs but also CSCs. Our
previous studyhas shown that cobalt chloride (CoCl2) was used to
treatdifferent cancer cell lines and daughter cells derived
fromPGCCs gained a mesenchymal phenotype [133]. When cul-tured with
adipogenesis medium, PGCCs can differentiateinto adipocytes
[133].
7.3. Molecular Mechanism of CSCs Differentiating intoAdipose.
The molecular mechanism of adipose differentia-tion of CSCs is
similar to that of MSCs. PPARγ activationis the key to adipocyte
differentiation of CSCs in vivo. Thephosphorylation of FOXO1 by AKT
inhibited the transcrip-tional activation of FOXO1 and activated
FOXO1 couldinhibit adipogenesis via PPARγ [80]. Activated AKT1
afterphosphorylation was of great significance to promote
adipo-genesis via mTORC2-AKT1-FOXC2 signal pathway [136].PI3K/AKT
plays an important role in maintaining the stem-ness of various
CSCs. The expression of OCT4 and Nanog in
8 Stem Cells International
-
breast CSCs depended on the PI3K/AKT pathway [137].Cytochrome c
oxidase 2 inducing the formation of CSCs inbreast cancer was
involved in the activation of PI3K andAKT [138]. Activating
PI3K/AKT signal pathway promotedthe initiation of liver CSCs [139].
Inhibition of PI3K/Akt/m-TOR pathway suppressed the stemness of
colon CSCs [140].AKT signal pathway plays an important role both in
the for-mation and differentiation of CSCs. The nuclear
oncoproteinMyc was a pivotal regulator in cell cycle regulation,
prolifer-ation, differentiation, and apoptosis [141, 142].
DeregulatedMyc expression was incompatible with terminal
differentia-tion in a variety of cell types, including adipocytes
[141].
PARP is a DNA repair enzyme and plays an importantrole in DNA
damage repair and apoptosis. PARP familymembers are associated with
CSC biology and its inhibition,including the development,
neurogenesis, and adipogenesisof stem cells. PARP1 and PARP2 are
crucial for adipocytedifferentiation and the regulation of lipid
accumulation[143]. PARP1 can keep the preadipocytes in the
stationaryphase of growth and inhibits the formation of
adipocytes[144]. PARP-1 can mediate poly-ADP-ribosylation
(PARyla-tion) of CEBPβ and PARylation is a posttranslational
modi-fication of proteins mediated by PARP family members.CEBPβ is
the crucial transcription factor in adipogenesis.The PARylation of
CEBPβ changes its DNA binding andtranscriptional activities and
thus inhibits the adipocytedifferentiation of stem cells. Depletion
or chemical inhibi-tion of PARP-1, or mutation of the PARylation
sites onC/EBPβ, promotes early adipogenesis [144]. PPARγ
bindingwith RXR forms different heterodimers plays a central role
inwhite adipose tissue (WAT) differentiation and
function,regulating the expression of key WAT proteins [145].PARP-2
is a member of the PPARγ/RXR transcriptionmachinery and a novel
cofactor of PPAR activity. PARP-2overexpression enhanced the basal
activity of PPARγ andPARP-2(-/-) mouse embryonic fibroblasts failed
to differen-tiate into adipocytes. In transient transfection
assays,PARP-2 siRNA decreases basal activity and ligand-dependent
activation of PPARγ. Chromatin immunoprecip-itation has shown a
DNA-dependent interaction of PARP-2and PPARγ/RXR heterodimer
[145].
7.4. Differentiation Therapy of Malignant Tumor. CSC-spe-cific
phenotypes and mechanisms indicate that CSCs maycontribute to the
failure of existing therapies to consistentlyeradicate malignant
tumors [146]. Differentiation of primi-tive cells within a
malignancy may lead to tumor degenera-tion and increased
susceptibility to conventional cytotoxicanticancer therapies [147].
Differentiation therapy has beenrecognized for a long time, and
potential strategies are thatinduce quiescent CSCs to differentiate
into more maturetumor cells. Results of Piccirillo et al. showed
that BMP4induced glioblastoma differentiation in mice models
ofhuman glioblastoma [148]. Modulation of CSC signalingpathways has
also shown the differentiation of CSCs inmedulloblastoma [149]. In
human breast cancer, Guptaet al. identified that potassium
ionophore and salinomycincould induce epithelial differentiation of
tumor cells andresult in inhibition of tumor growth [150]. In
addition, the
effects of the inhibitor and agonist for SIRT1/2 on the
induc-ing osteogenic differentiation indicated that SIRT1/2 had
animportant role in this process. Inducing differentiation ofcancer
cells may have potentially translational applicationsin the
treatment of SCLC [6]. EMT plays a critical role intumor formation
and differentiation. EMT is involved intumor metastasis and is
highly correlated with tumor pro-gression. Cancer cells undergo EMT
to exhibit a high degreeof plasticity, which many studies have
begun to exploit ther-apeutically by forcing the
transdifferentiation of EMT-derived cancer cells into benign cells.
Ishay-Ronen et al.showed that plasticity intrinsic to the EMT
program couldbe exploited to divert cancer cells into becoming
postmitoticadipocytes, thus preventing the metastases of cancer. A
cock-tail of rosiglitazone and BMP2 (a member of the transform-ing
growth factor β [TGF-β] superfamily) was shown toinfluence the
cells with mesenchymal phenotype, but not epi-thelial phenotype
[3]. The key step of adipocyte differentia-tion in tumors is the
same as that in MSCs with activationof the transcription factor
PPARγ. The study refers to stemcells derived from the breast cancer
microenvironment canbe induced differentiation by and their
impaired adipogene-sis. The PPARγ agonist thiazolidinedione delays
the invasiveprogression and induces adipose differentiation of
ductal car-cinoma in situ [3]. Adipose-derived stem cells could
beinduced into adipocytes by the PPARγ agonist thiazolidine-dione,
which was impaired by breast cancer microenviron-ment [151]. The
adipocytes derived from breast cancer cellsare truly functional
adipocytes. They express adipocyte-specific markers (such as C/EPB
genes, PPARγ2, FABP4)that show similar adipocyte metabolic and
transcriptomecharacteristics of adipocytes and lack mesenchymal
morpho-logical features. The induced cells strongly expressed
CEBPαand formed lipid droplets. Two FDA-approved drugs wereused to
treat animal xenografts from breast cancer cells.The two drugs are
a combination of rosiglitazone, a PPARinhibitor widely used to
treat diabetes, and trametinib, aMEK inhibitor. Compared with the
treatment drug trameti-nib alone, the combination treatment did not
significantlyinhibit tumor growth, but it significantly inhibited
tumorinvasion and metastasis. The combination treatment hadno toxic
effect on mice. Preclinical models further confirmedthe
effectiveness of this adipogenesis therapy. A high numberof human
adipocytes were detected in primary tumorstreated with the
combination of rosiglitazone and trametinib,and a significant
decrease was found in tumor cells metasta-sized to the lung
[3].
PARP inhibition can induce the transdifferentiation ofwhite
adipocytes to brown-like adipocytes, and the activityof PARP may be
a determinant of the differentiation ofthese adipocyte lineages
[152]. Olaparib, a potent PARPinhibitor used in clinical, can
induce white adipocytes totransdifferentiate into brown/beige
adipocytes with smallerlipid droplets. Olaparib can inhibit nuclear
and cytosolicpoly-ADP-ribose formation, induced NAD+/NADH ratio,and
consequently enhanced SIRT1 and AMPK activity[152]. PARP inhibitors
enhance the cytotoxic effects of anti-tumor drugs and radiotherapy
and selectively kill tumor cellswith homologous recombination
deficiency, such as BRCA1
9Stem Cells International
-
or BRCA2 mutations [153, 154]. Olaparib is the first
smallmolecule PARP inhibitor compound approved by the FDAand EMA to
enter the clinic in 2014 for the treatment ofadvanced-stage
BRCA1/2-mutated ovarian cancers. In aphase III clinical trial of
pancreatic cancer patients in 2019,Olaparib achieved positive
results in progression-free sur-vival [154, 155]. Rucaparib is an
inhibitor of PARP, and itdisrupts DNA repair and replication
pathways, leading tothe selective killing of cancer cells with
BRCA1/2 mutations[144]. In addition, the expression of S100A16 in
humanbreast cancer tissues was higher than in the paired
adjacentnoncancerous tissues. S100A16 is a calcium-binding
signal-ing protein, promotes adipogenesis, and involved in
weightgain attenuation induced by dietary calcium. Enhanced
adi-pogenesis with more lipid droplet density was clearlyobserved
in 3T3-L1 preadipocytes with overexpression ofS100A16 [156].
S100A16 promoted EMT by upregulatingthe transcription factors
Notch1, ZEB1, and ZEB2, whichhad the capacities to directly repress
the expression of epithe-lial markers E-cadherin and beta-catenin
but increase mesen-chymal markers N-cadherin and vimentin [5]. All
the resultsregarding differentiation therapy may hold great promise
fornew therapeutic strategies. Many targeted
differentiationtherapies for CSCs are currently undergoing
preclinical andclinical research with the aim of reducing tumor
recurrenceand metastatic spread.
8. Conclusions
Adipocyte differentiation is a complex process, and a series
ofmolecular and signaling pathways have been identified asinvolved
in regulating adipocyte differentiation. MSCs,which are recruited
from the vascular stroma of adipose tis-sue, provide the adipocyte
precursors. Members of the BMPandWnt families are key mediators of
stem cell commitmentto produce preadipocytes. In addition, exposure
of growth-arrested preadipocytes to differentiation inducers such
asIGF1, glucocorticoid, and cAMP triggers DNA replicationand
reentry into mitotic clonal expansion, which involves
atranscription factor cascade followed by the expression
ofadipocyte genes. Critical to these events are phosphorylationof
the transcription factor C/EBPβ by MAP kinase andGSK3β, and
activated C/EBPβ then triggers transcription ofPPARγ and C/EBPα,
which in turn coordinately activategenes whose expression produces
the adipocyte phenotype.
CSCs play an important fundamental role in tumor pro-gression
because of their tumorigenic properties, resistanceto radiation and
chemotherapy, invasiveness, and tendencyto evade immune responses,
which contribute to tumorrecurrence. The difficulty of targeting
CSCs lies in the intrin-sic properties of these cells and the
acquired phenotypesfollowing therapeutic interventions. These
characteristicsunderscore the importance of innovative treatment
options.Cell differentiation is an important pathway in tumor
trans-formation, and a better understanding of typical
differentia-tion factors may open the door to new therapeutic
strategiesthat regulate key differentiation pathways in
cancer.Although the understanding of the process of
adipocytedifferentiation has improved over the past 20 years,
many
questions remain. For example, how can adipocyte
differenti-ation be induced in vivo? How can the different
differentia-tion directions of pluripotent stem cells be balanced?
Canwe avoid diseases by influencing the adipocyte differentia-tion
of stem cells? Almost every important cellular signal-ing pathway
has a positive or negative effect on adipocytedevelopment, and some
pathways exert both pro- andantiadipogenic effects depending on
factors that are stillpoorly understood. Many targeted
differentiation therapiesfor CSCs are currently undergoing
preclinical and clinicalresearch with the aim of reducing
recurrence and metastaticspread. Current and future studies will
provide strongevidence for solving various problems and focus on
accuratetargets for the treatment of adipocyte
differentiation-relateddiseases. Studies about the molecular
mechanism and regula-tory proteins involved in adipocyte
differentiation of MSCsmay provide new therapeutic ideas and
targets for clinicalmalignant tumor differentiation therapy.
Abbreviations
MSCs: Mesenchymal stem cellsCSCs: Cancer stem cellsPGCCs:
Polyploid giant cancer cellsIBMX: 3-isobutyl-1-methylxanthineEMT:
Epithelial-to-mesenchymal transitionBRCA: Breast cancer
sususceptibility geneWDLPS: Well-differentiated liposarcomaDDLPS:
Dedifferentiated liposarcomaBMP: Bone morphogenetic proteinC/EBPs:
CCAAT enhancer-binding proteinsCHOP: C/EBP-homologous proteinCBP:
Cyclic AMP response element-binding
proteinFABP4: Fatty acid-binding protein 4PPARγ: Peroxisome
proliferator-activated receptor γPPRE: Peroxisome proliferator
response elementPPFP: PPARγ fusion proteinPARP: Poly ADP-ribose
polymeraseRXR: Retinoid X receptorIGF1: Insulin/insulin-like growth
factor 1TGF: Transforming growth factorTNF: Tumor necrosis
factorFGF: Fibroblast growth factorMMP: Matrix
metalloproteinaseSMAD: Drosophila mothers against
decapentaplegic
proteinERK: Extracellular regulated protein kinasesMAPK:
Mitogen-activated protein kinaseMKP1: Mitogen-activated protein
kinase phospha-
tase-1JAK-STAT3: Janus kinase-signal transducer and
activator
of transcription 3PI3K: Phosphoinositide 3-kinaseAKT/PKB:
Protein kinase BmTOR: Serine/threonine-protein kinaseKLF:
Krüppel-like factorsHH: HedgehogHDAC: Histone deacetylase
10 Stem Cells International
-
SREBP: Sterol-regulatory element-binding proteinsPref:
Preadipocyte factorGLUT4: Glucose transporter 4LSD1/KDM1: Lysine
specific demethylase 1 ASIRT1: sirtuin1sFRP: Secreted
frizzled-related proteinFOXO: Forkhead box protein OP300: Histone
acetyltransferase p300SETD: SET domain-containingHOX: Homeotic
genesLncRNA: Long noncoding RNAArp2/3: Actin-related protein
2/3PARylation: Poly-ADP-ribosylationEIF: Eukaryotic translation
initiation factorROS: Oxygen speciesAtg: Autophagy-related geneEBF:
Transcription factor CoeNCoR: Nuclear receptor corepressor.
Conflicts of Interest
The authors declare that there is no conflict of interest.
Authors’ Contributions
SZ designed the study, contributed to manuscript writing,and
approved the manuscript before submission. KZ, XY,and QZ collected
and analyzed data and approved themanuscript before submission. ZL,
FF, and HZ collected,analyzed, and interpreted data, and approved
the manuscriptbefore submission. MZ collected data, gave
constructivecomments on the manuscript, and approved the
manuscriptbefore submission. Kexin Zhang and Xudong Yang
contrib-uted equally to this work.
Acknowledgments
This work was supported in part by grants from the
NationalNatural Science Foundation of China (81672426) and
thefoundation of committee on science and technology of Tian-jin
(17ZXMFSY00120 and 17YFZCSY00700).
References
[1] K. Sarjeant and J. M. Stephens, “Adipogenesis,” Cold
SpringHarbor Perspectives in Biology, vol. 4, no. 9, article
a008417,2012.
[2] M. Zeniou, L. Nguekeu-Zebaze, and F. Dantzer,
“Therapeuticconsiderations of PARP in stem cell biology: relevance
in can-cer and beyond,” Biochemical Pharmacology, vol. 167,pp.
107–115, 2019.
[3] D. Ishay-Ronen, M. Diepenbruck, R. K. R. Kalathur et
al.,“Gain Fat–Lose Metastasis: Converting Invasive Breast Can-cer
Cells into Adipocytes Inhibits Cancer Metastasis,” CancerCell, vol.
35, no. 1, pp. 17–32.e6, 2019.
[4] G. B. Park, Y. H. Chung, J. H. Gong, D. H. Jin, and D.
Kim,“GSK-3β-mediated fatty acid synthesis enhances epithelialto
mesenchymal transition of TLR4-activated colorectal can-cer cells
through regulation of TAp63,” International Journalof Oncology,
vol. 49, no. 5, pp. 2163–2172, 2016.
[5] W. Zhou, H. Pan, T. Xia et al., “Up-regulation of
S100A16expression promotes epithelial-mesenchymal transition
viaNotch1 pathway in breast cancer,” Journal of BiomedicalScience,
vol. 21, no. 1, p. 97, 2014.
[6] Z. Zhang, Y. Zhou, H. Qian et al., “Stemness and
inducingdifferentiation of small cell lung cancer NCI-H446 cells,”
CellDeath & Disease, vol. 4, no. 5, article e633, 2013.
[7] P. Hallenborg, S. Feddersen, L. Madsen, and K.
Kristiansen,“The tumor suppressors pRB and p53 as regulators of
adi-pocyte differentiation and function,” Expert Opinion
onTherapeutic Targets, vol. 13, no. 2, pp. 235–246, 2008.
[8] U. Basu-Roy, E. Han, K. Rattanakorn et al., “PPARγ
agonistspromote differentiation of cancer stem cells by
restrainingYAP transcriptional activity,” Oncotarget, vol. 7, no.
38,pp. 60954–60970, 2016.
[9] M. E. Dobson, E. Diallo-Krou, V. Grachtchouk et al.,
“Pioglit-azone induces a proadipogenic antitumor response in
micewith PAX8-PPARgamma fusion protein thyroid
carcinoma,”Endocrinology, vol. 152, no. 11, pp. 4455–4465,
2011.
[10] Y. J. Kim, D. B. Yu, M. Kim, and Y. L. Choi,
“Adipogenesisinduces growth inhibition of dedifferentiated
liposarcoma,”Cancer Science, vol. 110, no. 8, pp. 2676–2683,
2019.
[11] H. G. Linhart, K. Ishimura-Oka, F. DeMayo et al.,
“C/EBPal-pha is required for differentiation of white, but not
brown,adipose tissue,” Proceedings of the National Academy of
Sci-ences of the United States of America, vol. 98, no. 22,pp.
12532–12537, 2001.
[12] L. Fajas, “Adipogenesis: a cross-talk between cell
proliferationand cell differentiation,” Annals of Medicine, vol.
35, no. 2,pp. 79–85, 2009.
[13] Q. Q. Tang and M. D. Lane, “Adipogenesis: from stem cell
toadipocyte,” Annual Review of Biochemistry, vol. 81, no. 1,pp.
715–736, 2012.
[14] D. Moseti, A. Regassa, and W. K. Kim, “Molecular
regulationof adipogenesis and potential anti-adipogenic bioactive
mol-ecules,” International Journal of Molecular Sciences, vol.
17,no. 1, p. 124, 2016.
[15] Q. Q. Tang, T. C. Otto, and M. D. Lane, “Mitotic
clonalexpansion: a synchronous process required for
adipogenesis,”Proceedings of the National Academy of Sciences of
the UnitedStates of America, vol. 100, no. 1, pp. 44–49, 2003.
[16] Y. C. Cho and C. R. Jefcoate, “PPAR?1 synthesis and
adipo-genesis in C3H10T1/2 cells depends on S-phase progression,but
does not require mitotic clonal expansion,” Journal ofCellular
Biochemistry, vol. 91, no. 2, pp. 336–353, 2004.
[17] E. D. Rosen and O. A. MacDougald, “Adipocyte
differentia-tion from the inside out,” Nature Reviews. Molecular
CellBiology, vol. 7, no. 12, pp. 885–896, 2006.
[18] I. Takada, A. P. Kouzmenko, and S. Kato, “Wnt and
PPARγsignaling in osteoblastogenesis and adipogenesis,”
NatureReviews Rheumatology, vol. 5, no. 8, pp. 442–447, 2009.
[19] C. Y. Logan and R. Nusse, “The Wnt signaling pathway
indevelopment and disease,” Annual Review of Cell and
Devel-opmental Biology, vol. 20, no. 1, pp. 781–810, 2004.
[20] C. N. Bennett, S. E. Ross, K. A. Longo et al., “Regulation
ofWnt signaling during adipogenesis,” The Journal of
BiologicalChemistry, vol. 277, no. 34, pp. 30998–31004, 2002.
[21] K. A. Longo, W. S. Wright, S. Kang et al., “Wnt10b
inhibitsdevelopment of white and brown adipose tissues,” The
Jour-nal of Biological Chemistry, vol. 279, no. 34, pp.
35503–35509, 2004.
11Stem Cells International
-
[22] Y. H. Tseng, A. J. Butte, E. Kokkotou et al., “Prediction
of pre-adipocyte differentiation by gene expression reveals role
ofinsulin receptor substrates and necdin,” Nature Cell Biology,vol.
7, no. 6, pp. 601–611, 2005.
[23] Y. H. Tseng, K. M. Kriauciunas, E. Kokkotou, and C. R.
Kahn,“Differential roles of insulin receptor substrates in brown
adi-pocyte differentiation,” Molecular and Cellular Biology,vol.
24, no. 5, pp. 1918–1929, 2004.
[24] A. Kanazawa, S. Tsukada, M. Kamiyama, T. Yanagimoto,M.
Nakajima, and S. Maeda, “Wnt5b partially inhibitscanonical Wnt/
β-catenin signaling pathway and promotesadipogenesis in 3T3-L1
preadipocytes,” Biochemical andBiophysical Research Communications,
vol. 330, no. 2,pp. 505–510, 2005.
[25] M. M. Cohen Jr., “The hedgehog signaling network,”
Ameri-can Journal of Medical Genetics. Part A, vol. 123A, no. 1,pp.
5–28, 2003.
[26] M. Varjosalo and J. Taipale, “Hedgehog: functions and
mech-anisms,” Genes & Development, vol. 22, no. 18, pp.
2454–2472, 2008.
[27] A. W. James, P. Leucht, B. Levi et al., “Sonic hedgehog
influ-ences the balance of osteogenesis and adipogenesis in
mouseadipose-derived stromal cells,” Tissue Engineering Part A,vol.
16, no. 8, pp. 2605–2616, 2010.
[28] S. Spinella-Jaegle, G. Rawadi, S. Kawai et al., “Sonic
hedgehogincreases the commitment of pluripotent mesenchymal
cellsinto the osteoblastic lineage and abolishes adipocytic
differ-entiation,” Journal of Cell Science, vol. 114, Part 11,pp.
2085–2094, 2001.
[29] W. Cousin, C. Fontaine, C. Dani, and P. Peraldi,
“Hedgehogand adipogenesis: fat and fiction,” Biochimie, vol. 89,
no. 12,pp. 1447–1453, 2007.
[30] C. Ge, W. P. Cawthorn, Y. Li, G. Zhao, O. A. MacDougald,and
R. T. Franceschi, “Reciprocal control of osteogenic andadipogenic
differentiation by ERK/MAP kinase phosphoryla-tion of Runx2 and
PPARγ transcription factors,” Journal ofCellular Physiology, vol.
231, no. 3, pp. 587–596, 2016.
[31] H. Sakaue, W. Ogawa, T. Nakamura, T. Mori, K. Nakamura,and
M. Kasuga, “Role of MAPK phosphatase-1 (MKP-1) inadipocyte
differentiation,” The Journal of Biological Chemis-try, vol. 279,
no. 38, pp. 39951–39957, 2004.
[32] E. D. Rosen, C. J. Walkey, P. Puigserver, and B. M.
Spiegel-man, “Transcriptional regulation of adipogenesis,” Genes
&Development, vol. 14, no. 11, pp. 1293–1307, 2000.
[33] P. Tontonoz, E. Hu, and B. M. Spiegelman, “Stimulation
ofadipogenesis in fibroblasts by PPAR gamma 2, a lipid-activated
transcription factor,” Cell, vol. 79, no. 7, pp. 1147–1156,
1994.
[34] Q. Tong, G. Dalgin, H. Xu, C. N. Ting, J. M. Leiden, and G.
S.Hotamisligil, “Function of GATA transcription factors
inpreadipocyte-adipocyte transition,” Science, vol. 290,no. 5489,
pp. 134–138, 2000.
[35] E. Mueller, S. Drori, A. Aiyer et al., “Genetic analysis of
adi-pogenesis through peroxisome proliferator-activated recep-tor γ
isoforms,” The Journal of Biological Chemistry,vol. 277, no. 44,
pp. 41925–41930, 2002.
[36] D. Ren, T. N. Collingwood, E. J. Rebar, A. P. Wolffe, and
H. S.Camp, “PPARgamma knockdown by engineered transcrip-tion
factors: exogenous PPARgamma2 but not PPAR-gamma1 reactivates
adipogenesis,” Genes & Development,vol. 16, no. 1, pp. 27–32,
2002.
[37] J. Zhang, M. Fu, T. Cui et al., “Selective disruption of
PPAR-gamma 2 impairs the development of adipose tissue and insu-lin
sensitivity,” Proceedings of the National Academy ofSciences of the
United States of America, vol. 101, no. 29,pp. 10703–10708,
2004.
[38] S. R. Farmer, “Transcriptional control of adipocyte
forma-tion,” Cell Metabolism, vol. 4, no. 4, pp. 263–273, 2006.
[39] R. J. Christy, K. H. Kaestner, D. E. Geiman, and M. D.
Lane,“CCAAT/enhancer binding protein gene promoter: bindingof
nuclear factors during differentiation of 3T3-L1 preadipo-cytes,”
Proceedings of the National Academy of Sciences of theUnited States
of America, vol. 88, no. 6, pp. 2593–2597, 1991.
[40] Y. Zuo, L. Qiang, and S. R. Farmer, “Activation of
CCAAT/enhancer-binding protein (C/EBP) alpha expression byC/EBP
beta during adipogenesis requires a
peroxisomeproliferator-activated receptor-gamma-associated
repressionof HDAC1 at the C/ebp alpha gene promoter,” The Journalof
Biological Chemistry, vol. 281, no. 12, pp. 7960–7967, 2006.
[41] E. D. Rosen, C. H. Hsu, X. Wang et al., “C/EBPalpha
inducesadipogenesis through PPARgamma: a unified pathway,”Genes
& Development, vol. 16, no. 1, pp. 22–26, 2002.
[42] Z. Wu, E. D. Rosen, R. Brun et al., “Cross-Regulation
ofC/EBPα and PPARγ Controls the Transcriptional Pathwayof
Adipogenesis and Insulin Sensitivity,” Molecular Cell,vol. 3, no.
2, pp. 151–158, 1999.
[43] A. K. El-Jack, J. K. Hamm, P. F. Pilch, and S. R.
Farmer,“Reconstitution of insulin-sensitive glucose transport
infibroblasts requires expression of both PPARγ and C/EBPα,”The
Journal of Biological Chemistry, vol. 274, no. 12,pp. 7946–7951,
1999.
[44] H. Huang, T. J. Song, X. Li et al., “BMP signaling pathway
isrequired for commitment of C3H10T1/2 pluripotent stemcells to the
adipocyte lineage,” Proceedings of the NationalAcademy of Sciences
of the United States of America,vol. 106, no. 31, pp. 12670–12675,
2009.
[45] S. E. Wheeler and N. Y. Lee, “Emerging roles of
transforminggrowth factor β signaling in diabetic retinopathy,”
Journal ofCellular Physiology, vol. 232, no. 3, pp. 486–489,
2017.
[46] M. Kawai and C. J. Rosen, “The IGF-I regulatory system
andits impact on skeletal and energy homeostasis,” Journal
ofCellular Biochemistry, vol. 111, no. 1, pp. 14–19, 2010.
[47] C. B. Sullivan, R. M. Porter, C. H. Evans et al., “TNFα and
IL-1β influence the differentiation and migration of murineMSCs
independently of the NF-κB pathway,” Stem CellResearch &
Therapy, vol. 5, no. 4, p. 104, 2014.
[48] D. Bauters, I. Scroyen, M. van Hul, and H. R. Lijnen,
“Gelati-nase A (MMP-2) promotes murine adipogenesis,” Biochi-mica
et Biophysica Acta, vol. 1850, no. 7, pp. 1449–1456,2015.
[49] S. Le Blanc, M. Simann, F. Jakob, N. Schütze, and T.
Schilling,“Fibroblast growth factors 1 and 2 inhibit adipogenesis
ofhuman bone marrow stromal cells in 3D collagen gels,”Experimental
Cell Research, vol. 338, no. 2, pp. 136–148,2015.
[50] Q. Q. Tang, T. C. Otto, and M. D. Lane, “Commitment
ofC3H10T1/2 pluripotent stem cells to the adipocyte
lineage,”Proceedings of the National Academy of Sciences of the
UnitedStates of America, vol. 101, no. 26, pp. 9607–9611, 2004.
[51] J. Massague, J. Seoane, and D. Wotton, “Smad
transcriptionfactors,” Genes & Development, vol. 19, no. 23,
pp. 2783–2810, 2005.
12 Stem Cells International
-
[52] L. Choy and R. Derynck, “Transforming growth
factor-betainhibits adipocyte differentiation by Smad3 interacting
withCCAAT/enhancer-binding protein (C/EBP) and repressingC/EBP
transactivation function,” The Journal of BiologicalChemistry, vol.
278, no. 11, pp. 9609–9619, 2003.
[53] L. Choy, J. Skillington, and R. Derynck, “Roles of
autocrineTGF-beta receptor and Smad signaling in adipocyte
differen-tiation,” The Journal of Cell Biology, vol. 149, no. 3,
pp. 667–682, 2000.
[54] N. I. zur Nieden, G. Kempka, D. E. Rancourt, and H.-J.
Ahr,“Induction of chondro-, osteo- and adipogenesis in embry-onic
stem cells by bone morphogenetic protein-2: effect ofcofactors on
differentiating lineages,” BMC DevelopmentalBiology, vol. 5, no. 1,
p. 1, 2005.
[55] E. A. Wang, D. I. Israel, S. Kelly, and D. P. Luxenberg,
“Bonemorphogenetic protein-2 causes commitment and differenti-ation
in C3Hl0T1/2 and 3T3 cells,” Growth Factors, vol. 9,no. 1, pp.
57–71, 2009.
[56] T. Mori, H. Sakaue, H. Iguchi et al., “Role of Krüppel-like
fac-tor 15 (KLF15) in transcriptional regulation of
adipogenesis,”The Journal of Biological Chemistry, vol. 280, no.
13,pp. 12867–12875, 2005.
[57] M. K. Jang, S. Lee, and M. H. Jung, “RNA-Seq analysis
revealsa negative role of KLF16 in adipogenesis,” PLoS One, vol.
11,no. 9, article e0162238, 2016.
[58] M. Asada, A. Rauch, H. Shimizu et al., “DNA
binding-dependent glucocorticoid receptor activity promotes
adipo-genesis via Krüppel-like factor 15 gene expression,”
Labora-tory Investigation, vol. 91, no. 2, pp. 203–215, 2011.
[59] Y. Oishi, I. Manabe, K. Tobe et al., “Krüppel-like
transcrip-tion factor KLF5 is a key regulator of adipocyte
differentia-tion,” Cell Metabolism, vol. 1, no. 1, pp. 27–39,
2005.
[60] H. Pei, Y. Yao, Y. Yang, K. Liao, and J. R. Wu,
“Kruppel-likefactor KLF9 regulates PPARγ transactivation at the
middlestage of adipogenesis,” Cell Death and Differentiation,vol.
18, no. 2, pp. 315–327, 2011.
[61] Z. Chen, J. I. Torrens, A. Anand, B. M. Spiegelman, and J.
M.Friedman, “Krox20 stimulates adipogenesis via C/EBPβ-dependent
and -independent mechanisms,” Cell Metabolism,vol. 1, no. 2, pp.
93–106, 2005.
[62] D. Li, S. Yea, S. Li et al., “Krüppel-like factor-6
promotes pre-adipocyte differentiation through histone deacetylase
3-dependent repression of DLK1,” The Journal of
BiologicalChemistry, vol. 280, no. 29, pp. 26941–26952, 2005.
[63] S. S. Banerjee, M. W. Feinberg, M. Watanabe et al.,
“TheKrüppel-like factor KLF2 inhibits peroxisome
proliferator-activated Receptor-γ expression and adipogenesis,” The
Jour-nal of Biological Chemistry, vol. 278, no. 4, pp.
2581–2584,2003.
[64] J. Yun, H. Jin, Y. Cao et al., “RNA-Seq analysis reveals a
pos-itive role of HTR2A in adipogenesis in Yan Yellow
Cattle,”International Journal of Molecular Sciences, vol. 19, no.
6,article 1760, 2018.
[65] N. Sue, B. H. A. Jack, S. A. Eaton et al., “Targeted
disruptionof the basic Krüppel-Like factor gene (Klf3) reveals a
role inadipogenesis,” Molecular and Cellular Biology, vol. 28,no.
12, pp. 3967–3978, 2008.
[66] W. Yang, C. Yang, J. Luo, Y. Wei, W. Wang, and Y.
Zhong,“Adiponectin promotes preadipocyte differentiation via
thePPARγ pathway,” Molecular Medicine Reports, vol. 17,no. 1, pp.
428–435, 2018.
[67] J. M. Stephens, R. F. Morrison, and P. F. Pilch, “The
expres-sion and regulation of STATs during 3T3-L1 adipocyte
dif-ferentiation,” The Journal of Biological Chemistry, vol.
271,no. 18, pp. 10441–10444, 1996.
[68] Z. E. Floyd and J. M. Stephens, “STAT5A promotes
adipo-genesis in nonprecursor cells and associates with the
gluco-corticoid receptor during adipocyte
differentiation,”Diabetes, vol. 52, no. 2, pp. 308–314, 2003.
[69] P. Gao, Y. Zhang, Y. Liu et al., “Signal transducer and
activa-tor of transcription 5B (STAT5B) modulates adipocyte
differ-entiation via MOF,” Cellular Signalling, vol. 27, no. 12,pp.
2434–2443, 2015.
[70] D. Annamalai and N. A. Clipstone, “Prostaglandin
F2αinhibits adipogenesis via an autocrine-mediated
interleukin-11/glycoprotein 130/STAT1-dependent signaling
cascade,”Journal of Cellular Biochemistry, vol. 115, no. 7, pp.
1308–1321, 2014.
[71] X. Hu, Y. Zhou, Y. Yang et al., “Identification of zinc
fingerprotein Bcl6 as a novel regulator of early adipose
commit-ment,” Open Biology, vol. 6, no. 6, article 160065,
2016.
[72] M. A. Meraz, J. M. White, K. C. F. Sheehan et al.,
“TargetedDisruption of the Stat1 Gene in Mice Reveals
UnexpectedPhysiologic Specificity in the JAK -STAT Signaling
Pathway,”Cell, vol. 84, no. 3, pp. 431–442, 1996.
[73] Y. Yuan, Y. Xi, J. Chen et al., “STAT3 stimulates
adipogenicstem cell proliferation and cooperates with HMGA2
duringthe early stage of differentiation to promote
adipogenesis,”Biochemical and Biophysical Research
Communications,vol. 482, no. 4, pp. 1360–1366, 2017.
[74] E. R. Cernkovich, J. Deng, M. C. Bond, T. P. Combs, and J.
B.Harp, “Adipose-specific disruption of signal transducer
andactivator of transcription 3 increases body weight and
adi-posity,” Endocrinology, vol. 149, no. 4, pp.
1581–1590,2008.
[75] S. Teglund, C. McKay, E. Schuetz et al., “Stat5a and
Stat5bproteins have essential and nonessential, or redundant,
rolesin cytokine responses,” Cell, vol. 93, no. 5, pp. 841–850,
1998.
[76] Y. Zhou, J. Peng, and S. Jiang, “Role of histone
acetyltransfer-ases and histone deacetylases in adipocyte
differentiation andadipogenesis,” European Journal of Cell Biology,
vol. 93, no. 4,pp. 170–177, 2014.
[77] C. M. Bäckesjö, Y. Li, U. Lindgren, and L. A. Haldosén,
“Acti-vation of Sirt1 decreases adipocyte formation during
osteo-blast differentiation of mesenchymal stem cells,” Journal
ofBone and Mineral Research, vol. 21, no. 7, pp. 993–1002,2006.
[78] Y. Zhou, T. Song, J. Peng et al., “SIRT1 suppresses
adipogen-esis by activating Wnt/β-catenin signaling in vivo andin
vitro,” Oncotarget, vol. 7, no. 47, pp. 77707–77720, 2016.
[79] X. J. Yang and E. Seto, “Lysine acetylation: codified
crosstalkwith other posttranslational modifications,” Molecular
Cell,vol. 31, no. 4, pp. 449–461, 2008.
[80] J. Chen, Y. Lu, M. Tian, and Q. Huang, “Molecular
mecha-nisms of FOXO1 in adipocyte differentiation,” Journal
ofMolecular Endocrinology, vol. 62, no. 3, pp. R239–R253, 2019.
[81] E. Jing, S. Gesta, and C. R. Kahn, “SIRT2 regulates
adipocytedifferentiation through FoxO1
acetylation/deacetylation,”Cell Metabolism, vol. 6, no. 2, pp.
105–114, 2007.
[82] R. M. Evans, G. D. Barish, and Y. X. Wang, “PPARs and
thecomplex journey to obesity,” Nature Medicine, vol. 10,no. 4, pp.
355–361, 2004.
13Stem Cells International
-
[83] J. E. Dominy and P. Puigserver, “Nuclear FoxO1
inflamesinsulin resistance,” The EMBO Journal, vol. 29, no. 24,pp.
4068-4069, 2010.
[84] L. Qiang, L. Wang, N. Kon et al., “Brown remodeling of
whiteadipose tissue by SirT1-dependent deacetylation of
Pparγ,”Cell, vol. 150, no. 3, pp. 620–632, 2012.
[85] M. M. Musri, M. C. Carmona, F. A. Hanzu, P. Kaliman,R.
Gomis, and M. Párrizas, “Histone demethylase LSD1 reg-ulates
adipogenesis,” The Journal of Biological Chemistry,vol. 285, no.
39, pp. 30034–30041, 2010.
[86] K.Wakabayashi, M. Okamura, S. Tsutsumi et al., “The
perox-isome proliferator-activated receptor gamma/retinoid
Xreceptor alpha heterodimer targets the histone modificationenzyme
PR-Set7/Setd8 gene and regulates adipogenesisthrough a positive
feedback loop,” Molecular and CellularBiology, vol. 29, no. 13, pp.
3544–3555, 2009.
[87] L.Wang, Q. Jin, J. E. Lee, I. H. Su, and K. Ge, “Histone
H3K27methyltransferase Ezh2 represses Wnt genes to facilitate
adi-pogenesis,” Proceedings of the National Academy of Sciencesof
the United States of America, vol. 107, no. 16, pp. 7317–7322,
2010.
[88] Z. Fan, T. Yamaza, J. S. Lee et al., “BCOR regulates
mesenchy-mal stem cell function by epigenetic mechanisms,”
NatureCell Biology, vol. 11, no. 8, pp. 1002–1009, 2009.
[89] J. Chen, Y. Liu, S. Lu et al., “The role and possible
mechanismof lncRNA U90926 in modulating 3T3-L1 preadipocyte
dif-ferentiation,” International Journal of Obesity, vol. 41, no.
2,pp. 299–308, 2017.
[90] K. Kajimoto, H. Naraba, and N. Iwai, “MicroRNA and 3T3-L1
pre-adipocyte differentiation,” RNA, vol. 12, no. 9,pp. 1626–1632,
2006.
[91] H. Xie, B. Lim, and H. F. Lodish, “MicroRNAs induced
dur-ing adipogenesis that accelerate fat cell development
aredownregulated in obesity,” Diabetes, vol. 58, no. 5,pp.
1050–1057, 2009.
[92] J. A. Kennell, I. Gerin, O. A. MacDougald, and K.M.
Cadigan,“The microRNA miR-8 is a conserved negative regulator ofWnt
signaling,” Proceedings of the National Academy of Sci-ences of the
United States of America, vol. 105, no. 40,pp. 15417–15422,
2008.
[93] D. Hamam, D. Ali, M. Kassem, A. Aldahmash, and N. M.Alajez,
“microRNAs as regulators of adipogenic differentia-tion of
mesenchymal stem cells,” Stem Cells and Develop-ment, vol. 24, no.
4, pp. 417–425, 2015.
[94] E. K. Lee, M. J. Lee, K. Abdelmohsen et al., “miR-130
sup-presses adipogenesis by inhibiting peroxisome
proliferator-activated receptor gamma expression,” Molecular and
Cellu-lar Biology, vol. 31, no. 4, pp. 626–638, 2011.
[95] Z. Yuan, Q. Li, S. Luo et al., “PPARγ; and Wnt signaling
inadipogenic and osteogenic differentiation of mesenchymalstem
cells,” Current Stem Cell Research & Therapy, vol. 11,no. 3,
pp. 216–225, 2016.
[96] E. Eklund, “The role of Hox proteins in
leukemogenesis:insights into key regulatory events in
hematopoiesis,” CriticalReviews in Oncogenesis, vol. 16, no. 1-2,
pp. 65–76, 2011.
[97] X. X. Zhu, Y. W. Yan, D. Chen et al., “Long non-coding
RNAHoxA-AS3 interacts with EZH2 to regulate lineage commit-ment of
mesenchymal stem cells,” Oncotarget, vol. 7, no. 39,pp.
63561–63570, 2016.
[98] Y. Huang, Y. Zheng, C. Jin, X. Li, L. Jia, and W. Li,
“LongNon-coding RNA H19 Inhibits Adipocyte Differentiation of
Bone Marrow Mesenchymal Stem Cells through EpigeneticModulation
of Histone Deacetylases,” Scientific Reports,vol. 6, no. 1, article
28897, 2016.
[99] M. Li, X. Sun, H. Cai et al., “Long non-coding RNA
ADNCRsuppresses adipogenic differentiation by targeting
miR-204,”Biochimica et Biophysica Acta, vol. 1859, no. 7, pp.
871–882,2016.
[100] R. Gernapudi, B. Wolfson, Y. Zhang et al., “MicroRNA
140promotes expression of long noncoding RNA NEAT1 in
adi-pogenesis,” Molecular and Cellular Biology, vol. 36, no. 1,pp.
30–38, 2016.
[101] L. Mi, X. Y. Zhao, S. Li, G. Yang, and J. D. Lin,
“Conservedfunction of the long noncoding RNA Blnc1 in brown
adipo-cyte differentiation,” Molecular Metabolism, vol. 6, no.
1,pp. 101–110, 2017.
[102] E. Zhu, J. Zhang, Y. Li, H. Yuan, J. Zhou, and B. Wang,
“Longnoncoding RNAPlnc1controls adipocyte differentiation
byregulating peroxisome proliferator-activated receptor γ,”The
FASEB Journal, vol. 33, no. 2, pp. 2396–2408, 2018.
[103] M.Wang and R. J. Kaufman, “The impact of the
endoplasmicreticulum protein-folding environment on cancer
develop-ment,” Nature Reviews Cancer, vol. 14, no. 9, pp.
581–597,2014.
[104] C. E. Lowe, R. J. Dennis, U. Obi, S. O'Rahilly, and J. J.
Roch-ford, “Investigating the involvement of the ATF6α pathwayof
the unfolded protein response in adipogenesis,” Interna-tional
Journal of Obesity, vol. 36, no. 9, pp. 1248–1251, 2012.
[105] T. P. T. Pham, J. Kwon, and J. Shin, “Berberine exerts
anti-adipogenic activity through up-regulation of C/EBP
inhibi-tors, CHOP and DEC2,” Biochemical and BiophysicalResearch
Communications, vol. 413, no. 2, pp. 376–382, 2011.
[106] J. Han, R. Murthy, B. Wood et al., “ER stress
signallingthrough eIF2α and CHOP, but not IRE1α, attenuates
adipo-genesis in mice,” Diabetologia, vol. 56, no. 4, pp.
911–924,2013.
[107] F. Atashi, A. Modarressi, and M. S. Pepper, “The role of
reac-tive oxygen species in mesenchymal stem cell adipogenic
andosteogenic differentiation: a review,” Stem Cells and
Develop-ment, vol. 24, no. 10, pp. 1150–1163, 2015.
[108] T. Lonergan, C. Brenner, and B. Bavister,
“Differentiation-related changes in mitochondrial properties as
indicators ofstem cell competence,” Journal of Cellular
Physiology,vol. 208, no. 1, pp. 149–153, 2006.
[109] A. H. Kramer, R. Kadye, P. S. Houseman, and E.
Prinsloo,“Mitochondrial STAT3 and reactive oxygen species: a
ful-crum of adipogenesis?,” Jakstat, vol. 4, no. 2,
articlee1084084, 2015.
[110] K. Schröder, K. Wandzioch, I. Helmcke, and R. P.
Brandes,“Nox4 acts as a switch between differentiation and
prolifera-tion in preadipocytes,” Arteriosclerosis, Thrombosis, and
Vas-cular Biology, vol. 29, no. 2, pp. 239–245, 2009.
[111] S. Hwang, J. W. Byun, J. S. Yoon, and E. J. Lee,
“Inhibitoryeffects of α-Lipoic acid on oxidative stress-induced
adipogen-esis in orbital fibroblasts from patients with graves
ophthal-mopathy,” Medicine (Baltimore), vol. 95, no. 2,
articlee2497, 2016.
[112] K. V. Tormos, E. Anso, R. B. Hamanaka et al.,
“Mitochondrialcomplex III ROS regulate adipocyte differentiation,”
CellMetabolism, vol. 14, no. 4, pp. 537–544, 2011.
[113] S. Furukawa, T. Fujita, M. Shimabukuro et al., “Increased
oxi-dative stress in obesity and its impact on metabolic
14 Stem Cells International
-
syndrome,” The Journal of Clinical Investigation, vol. 114,no.
12, pp. 1752–1761, 2004.
[114] H. Yan, E. Aziz, G. Shillabeer et al., “Nitric oxide
promotesdifferentiation of rat white preadipocytes in culture,”
Journalof Lipid Research, vol. 43, no. 12, pp. 2123–2129, 2002.
[115] R. Singh, S. Kaushik, Y. Wang et al., “Autophagy
regulateslipid metabolism,” Nature, vol. 458, no. 7242, pp.
1131–1135, 2009.
[116] R. Baerga, Y. Zhang, P. H. Chen, S. Goldman, and S. V.
Jin,“Targeted deletion of autophagy-related 5 (atg5) impairs
adi-pogenesis in a cellular model and in mice,” Autophagy, vol.
5,no. 8, pp. 1118–1130, 2014.
[117] C. Zhang, Y. He, M. Okutsu et al., “Autophagy is involved
inadipogenic differentiation by repressesing proteasome-dependent
PPARγ2 degradation,” American Journal of Phys-iology. Endocrinology
and Metabolism, vol. 305, no. 4,pp. E530–E539, 2013.
[118] Y. Zhang, S. Goldman, R. Baerga, Y. Zhao, M. Komatsu,
andS. Jin, “Adipose-specific deletion of autophagy-related gene
7(atg7) in mice reveals a role in adipogenesis,” Proceedings ofthe
National Academy of Sciences of the United States ofAmerica, vol.
106, no. 47, pp. 19860–19865, 2009.
[119] L. Guo, J. X. Huang, Y. Liu et al., “Transactivation of
Atg4b byC/EBPβ promotes autophagy to facilitate
adipogenesis,”Molecular and Cellular Biology, vol. 33, no. 16, pp.
3180–3190, 2013.
[120] J. Wu, X. Deng, J. Gao et al., “Autophagy mediates the
secre-tion of macrophage migration inhibitory factor from
cardio-myocytes upon serum-starvation,” Science China.
LifeSciences, vol. 62, no. 8, pp. 1038–1046, 2019.
[121] J. R. Hahm, M. Ahmed, and D. R. Kim,
“RKIPphosphorylation-dependent ERK1 activation stimulates
adi-pogenic lipid accumulation in 3T3-L1 preadipocytes
overex-pressing LC3,” Biochemical and Biophysical
ResearchCommunications, vol. 478, no. 1, pp. 12–17, 2016.
[122] H. Li, Y. Cheng, W. Wu et al., “SRSF10 regulates
alternativesplicing and is required for adipocyte
differentiation,”Molec-ular and Cellular Biology, vol. 34, no. 12,
pp. 2198–2207,2014.
[123] M. E. Huot, G. Vogel, A. Zabarauskas et al., “The
Sam68STAR RNA-binding protein regulates mTOR alternativesplicing
during adipogenesis,” Molecular Cell, vol. 46, no. 2,pp. 187–199,
2012.
[124] B. MEI, L. ZHAO, L. CHEN, and H. S. SUL, “Only the
largesoluble form of preadipocyte factor-1 (Pref-1), but not
thesmall soluble and membrane forms, inhibits adipocyte
differ-entiation: role of alternative splicing,” The Biochemical
Jour-nal, vol. 364, no. 1, Part 1, pp. 137–144, 2002.
[125] R. McBeath, D. M. Pirone, C. M. Nelson, K. Bhadriraju,
andC. S. Chen, “Cell shape, cytoskeletal tension, and RhoA
regu-late stem cell lineage commitment,” Developmental Cell,vol. 6,
no. 4, pp. 483–495, 2004.
[126] H. Nobusue, N. Onishi, T. Shimizu et al., “Regulation
ofMKL1 via actin cytoskeleton dynamics drives adipocyte
dif-ferentiation,” Nature Communications, vol. 5, no. 1,
article3368, 2014.
[127] B. Sen, Z. Xie, N. Case et al., “mTORC2 regulates
mechan-ically induced cytoskeletal reorganization and lineage
selec-tion in marrow-derived mesenchymal stem cells,” Journalof
Bone and Mineral Research, vol. 29, no. 1, pp. 78–89,2014.
[128] W. Yang, S. Thein, C. Y. Lim et al., “Arp2/3 complex
regulatesadipogenesis by controlling cortical actin remodelling,”
TheBiochemical Journal, vol. 464, no. 2, pp. 179–192, 2014.
[129] L. V. Nguyen, R. Vanner, P. Dirks, and C. J. Eaves,
“Cancerstem cells: an evolving concept,” Nature Reviews Cancer,vol.
12, no. 2, pp. 133–143, 2012.
[130] A. Kreso and J. E. Dick, “Evolution of the cancer stem
cellmodel,” Cell Stem Cell, vol. 14, no. 3, pp. 275–291, 2014.
[131] W. Chen, J. Dong, J. Haiech, M. C. Kilhoffer, and M.
Zeniou,“Cancer stem cell quiescence and plasticity as major
chal-lenges in cancer therapy,” Stem Cells International,vol. 2016,
Article ID 1740936, 16 pages, 2016.
[132] D. Contador, F. Ezquer, M. Espinosa et al.,
“Dexamethasoneand rosiglitazone are sufficient and necessary for
producingfunctional adipocytes from mesenchymal stem cells,”
Experi-mental Biology and Medicine (Maywood, N.J.), vol. 240, no.
9,pp. 1235–1246, 2015.
[133] S. Zhang, I. Mercado-Uribe, Z. Xing, B. Sun, J. Kuang,
andJ. Liu, “Generation of cancer stem-like cells through the
for-mation of polyploid giant cancer cells,” Oncogene, vol. 33,no.
1, pp. 116–128, 2014.
[134] Y. Liu, R. Zhang, J. Xin et al., “Identification of
S100A16 as anovel adipogenesis promoting factor in 3T3-L1 cells,”
Endo-crinology, vol. 152, no. 3, pp. 903–911, 2011.
[135] R. Virchow, “The Huxley lecture on recent advances in
sci-ence and their bearing on medicine and surgery: deliveredat the
opening of the Charing Cross Hospital Medical Schoolon October
3rd,” British Medical Journal, vol. 2, no. 1971,pp. 1021–1028,
1898.
[136] Y. Yao, M. Suraokar, B. G. Darnay et al., “BSTA
promotesmTORC2-mediated phosphorylation of Akt1 to
suppressexpression of FoxC2 and stimulate adipocyte
differentiation,”Science Signaling, vol. 6, no. 257, p. ra2,
2013.
[137] S. Almozyan, D. Colak, F. Mansour et al., “PD-L1
promotesOCT4 and Nanog expression in breast cancer stem cells
bysustaining PI3K/AKT pathway activation,” InternationalJournal of
Cancer, vol. 141, no. 7, pp. 1402–1412, 2017.
[138] M. Majumder, X. Xin, L. Liu et al., “COX-2 induces
breastcancer stem cells via EP4/PI3K/AKT/NOTCH/WNT axis,”Stem
Cells, vol. 34, no. 9, pp. 2290–2305, 2016.
[139] M. Zhu, W. Li, Y. Lu et al., “HBx drives alpha
fetoproteinexpression to promote initiation of liver cancer stem
cellsthrough activating PI3K/AKT signal pathway,”
InternationalJournal of Cancer, vol. 140, no. 6, pp. 1346–1355,
2017.
[140] J. Chen, R. Shao, F. Li et al., “PI3K/Akt/mTOR pathway
dualinhibitor BEZ235 suppresses the stemness of colon cancerstem
cells,” Clinical and Experimental Pharmacology & Phys-iology,
vol. 42, no. 12, pp. 1317–1326, 2015.
[141] V. J. Heath, D. A. F. Gillespie, and D. H. Crouch,
“Inhibitionof the terminal stages of adipocyte differentiation by
cMyc,”Experimental Cell Research, vol. 254, no. 1, pp. 91–98,
2000.
[142] F. Fei, J. Qu, K. Liu et al., “The subcellular location of
cyclinB1 and CDC25 associated with the formation of polyploidgiant
cancer cells and their clinicopathological significance,”Laboratory
Investigation, vol. 99, no. 4, pp. 483–498, 2019.
[143] M. Szanto and P. Bai, “The role of ADP-ribose metabolism
inmetabolic regulation, adipose tissue differentiation,
andmetabolism,” Genes & Development, vol. 34, no. 5-6,pp.
321–340, 2020.
[144] K. Y. Lin and W. L. Kraus, “PARP inhibitors for cancer
ther-apy,” Cell, vol. 169, no. 2, p. 183, 2017.
15Stem Cells International
-
[145] P. Bai, S. M. Houten, A. Huber et al.,
“Poly(ADP-ribose)polymerase-2 [corrected] controls adipocyte
differentiationand adipose tissue function through the regulation
of theactivity of the retinoid X receptor/peroxisome
proliferator-activated receptor-gamma [corrected] heterodimer,”
TheJournal of Biological Chemistry, vol. 282, no. 52, pp.
37738–37746, 2007.
[146] N. Y. Frank, T. Schatton, and M. H. Frank, “The
therapeuticpromise of the cancer stem cell concept,” The Journal of
Clin-ical Investigation, vol. 120, no. 1, pp. 41–50, 2010.
[147] G. B. Pierce, “The cancer cell and its control by the
embryoRous-Whipple Award lecture,” The American Journal
ofPathology, vol. 113, no. 1, pp. 117–124, 1983.
[148] S. G. M. Piccirillo, B. A. Reynolds, N. Zanetti et al.,
“B